The Popular Science Review: A Quarterly Miscellany of Entertaining and ...

shown by Schifi‘ that, after section of the anterior roots, all the muscular nerves after a while are found in a state of degeneration. The knowledge of the position of the limbs may come from the nerves of the tendons and of the soft parts about the joints. In a comparatively recent number of the “ Archivfiir Nervenkrankheiten," M. Bernhardt describes how he arranged some pulleys at the foot of a bed, so that an unseen weight might be raised by the hand or foot. The experimenter determined first with what accuracy he could estimate the weight attached to'the cord when raised by voluntary motions. Then he caused the muscles to contract by electric stimulus, and found that, in the absence of a volitional impulse, it was much harder to tell how much weight was raised.

Irritabnhty of the Heart cf the Frog.—The “Lens,” in its last number, has ashort note on this subject. It says of Batrachians generally that besides being obliged to pump air down into their own lungs, which explains why the gular membrane underneath the under jaw is so elastic, acting on the volume of inhaled air in the cavity of the mouth on the mechanical principle of bellows, they catch game with the point of the tongue, drink through the spongy texture of the skin on the back, and live months in succession concealed in the mud bed of a pool without respiring; and yet the systole and diastole, or in plainer words, the contraction and expansion of the heart, is not suspended. Their vitality is remarkable, since the small amount of oxygen introduced into the arterial blood when making the final plunge in autumn keeps the spark of life alive till emerging from the water in the spring. If the heart of a frog is cut from its connections within the pericardium and placed on a table, it will pulsate and throb energetically for some minutes. When apparently quiescent, the point of a needle will rouse it again into spasmodic energy. Finally, by the touch of irritants, its irritability is completely exhausted. After experimenting full half an hour in that manner, we were struck with the lively vaultings of the frog from which the heart had been taken. Certainly it was conscious of its relations, for it avoided many cautious attempts to capture it on the part of the operator. It was some hours before death closed the scene. The vital tenacity of reptiles, particularly batrachians and chelonians, which include the tortoise family, is remarkable, and worthy of more extended scientific investigation.

Action of Certain Substances on the Spinal Cord.~—The “ Lancet,” in a late number, has an important article on the influence of substances on the reflex excitability of the cord. It states that Dr. S. Meihuizen gives, in Pfliiger’s “ Archiv ” (Band vii ., Heft 4 and 5),the results of a series of experiments he has made on the effects of various agents on the reflex irritability of the spinal cord. The animals were chiefly frogs, and the disturbing influence of the brain was removed by section of the cord below the medulla oblongata. The test of the degree of irritability of the spinal cord was in most instances very dilute (% per cent.) sulphuric acid, which was applied to the surface of the skin at intervals of aquarter of an hour, and the time before contraction occurred noted. Meihuizen finds that bromide of potassium rapidly depresses the excitability of the spinal cord, and ultimately entirely abolishes it, and he gives certain experiments which show that it is not due to the action of this salt on the periphery, or on the nerve cords,
but upon the cord itself. The salts of zinc have a similar action. He considers the acetate might properly be regarded as a narcotic. ' Chloral hydrate lowers the reflex activity, and its action is also central. Experiments with slrychm'a brought out the curious fact that whilst the nerves and muscles become highly sensitive to mechanical irritation, thereis no material increase in their reaction upon the application of chemical stimuli. Quim'ne, even in moderate doses, rapidly diminishes, and ultimately extinguishes, the reflex activity of the cord; but this action is apparently not direct, but in great measure indirect, through disturbance of the circulation and arrest of the heart’s action. Alcohol (ten per cent.) first and for a long time greatly lowered and then exalted the irritability of the spinal cord. Cajein rapidly lowered it (% c. c. of 10 per cent), almost entirely abolishing it in four hours. Mmphia first depressed, then exalted, and finally abolished the excitability of the cord. Digitalis has no influence on the spinal cord as a centre, but it acts as a depressant upon it, through its action on the vasomotor system.

Inguiry into the Antecedents of Sckntg'fic Men.—The “Medical Record,” which continues to supply most interesting information, says that following out a line of inquiry suggested by the remarkably interesting recent work of M. Decandolle, Mr. Francis, F.A.S., has issued a schedule of minute and searching questions as to their personal and family antecedents to about 250 of the most eminent scientific men in the United Kingdom. The object is to set forth the influence through which the dispositions of original workers in science have most commonly been formed, and have afterwards been trained and confirmed. The inquiry is one of much interest, and a considerable amount of curious information is sure to be obtained in this way.

The Nerve Supply of the Lachrymal Gland—It appears that in his experiments in this direction Dr. Demtschenko (Pfliiger’s “Archiv,” Sept. 1872) has operated on animals narcotised by means of morphia. The subjects were dogs, cats, and rabbits. The electric stimulus was applied by means of DuBois Reymond’s apparatus. The quantity of fluid discharged by the lachrymal glands was estimated by the number of square centimetres of blotting-paper that were moistened. In the dog and cat the lachrymal nerve could be reached from the orbit; but in the rabbit the skull had to be opened. The chief results obtained by Demtschenko (vide “ Lancet ”) were that the temporo-malar nerve exercises no influence on the lachrymal gland. Excitation of the great sympathetic augments the secretion; it augments also the quantity of fluid secreted by the conjunctiva, even when the nerve is irritated after ablation of the gland. The augmented flow of tears which follows irritation of a large number of cranial nerves (as the frontal, infra-orbital, nasal, lingual glosso-pharyngea], and pneumogastric) is not interfered with by section of the sympathetic, but is stopped directly by section of the lachrymal. This reflex action is not wholly abolished during the sleep induced by chloroform. The author proceeds to compare the results of irritation of the sympathetic and of the fifth on the quantity and quality of the tears. The great violence requisite to expose the fifth throws a doubt upon the value of these experiments. The tears, however, were clear and limpid when the fifth was irritated, but cloudy when the
sympathetic was excited. On the whole he thinks he may conclude from these and other experiments that the great sympathetic presides over the normal humectation of the globe of the eye; and this is supported by patho— logical facts, since the eyes of patients suffering from paralysis of the fifth retain their proper moisture, though the power of shedding tears is abolished. Disturbances of the circulation caused variations in the lachrymal secretion. After ligature of the carotoid artery, irritation of the lachrymal nerve caused a less abundant flow of tears than on the sound side. Ligature of the veins increased the flow of tears. All troubles of the respiration caused increased flow. '

Alcoholism detected by Increase in Temperature—Mr. Magnan, says the “Medical Record,” quoted from the “Gazette Hebdom,” points out signs which distinguish the serious from the passing form of acute alcoholism, and establish the prognosis. The most important is the course of the tem-, perature. In grave cases it rises from 104.40 F ahr. to 102.2'0 Fahr. on the first day, and goes on to 104° F ahr. and 107.5° Fahr., and in one case reached 110° Fahr. before death. In cases ending in recovery, the temperature during the first four or five days oscillates towards defervesence ; when during two or three days the temperature oscillates around 86° Fahr., the case is simple and recovery may be expected. Another sign to which M. Magnan attaches importance is the existence not only of the ordinary “ tremblingsfl but of muscular .tremors—fibrillar contractions—produced on pressure or percussion, and during sleep, as well in the deep as in the superficial muscles. This is of unfavourable omen.

How dg'fl‘erent Agents afect the Secretion of Bile—Dr. Stricker has recently made some experiments on this subject which are decidedly of interest. In a paper read before the Gesellschaf der Aerzte, the defects of the former methods of obtaining the secretion were pointed out. and a new method suggested by which a canula was introduced into the ductus communis choledochus; from this depended a flexible caoutchouc tube, which ended in a mouthpiece that was kept constantly at the same level in a vice, thus avoiding apparent variation due to different height of the orifice of exit. These experiments showed that all circumstances causing hypereemia of the blood-vessels of the liver increased the secretion of bile; whilst, on the contrary, all circumstances producing anaemia caused diminution. Thus the secretion was arrested in fasting animals, whilst it augmented after food “Tater introduced into the stomach or intestines caused a slight but transient increase. The introduction of purgative medicines, as croton oil, colocynth, jalap, calomel, Epsom salts, &c., materially increased the secretion of bile. It was at once stopped by ligature of the vena portae and vena hepatica. Ligature of the hepatic vein alone materially diminished the secretion ; ligature of the aorta at the diaphragm materially diminished the secretion, but did not entirely stop it; ligature below the origin of the cceliac artery augmented it; ligature of the vena cava ascendens immediately caused stoppage of the biliary secretion. All circumstances causing contraction of the vessels diminished the amount of secretion, as, for example, irritation of an exposed nerve, division of the spinal cord just below the medulla oblongata, and injection of strychnia. '

METALLURGY, MINERALOGY, AND MINING.

The Specific Gravity of Rubies and Diamonda—Mr. Greville Williams, F.R.S., says that in his paper entitled “ Researches on Emeralds and Beryls,"* he stated that the artificial rubies made by him by Gaudin’s process had a lower specific gravity than that of the true ruby. He there assumed the density of the ruby to be 353, on the authority of Brissonfi and that of the sapphire as 356, according to Muschenbroek.1 Having occasion, in extending his experiments on the subject, to take the specific gravity of several rubies and sapphires, he found their density to be very much higher than the numbers given in Gmelin’s “Chemistry.” On referring to other works,§ he found the numbers given in them to be generally between 39 and 4'0; Prof. Church also found a blue sapphire to have a density of 3979, and a. yellow one 4030. His own determinations, made upon very fine stones, gave him for rubies 3'95, and for sapphires 3'98. Assuming 3'95 as the average specific gravity of the ruby, it will be seen that Gaudin’s rubies, as first made by him (\Villiams), were 05 lower in density than the native ruby, instead of 008 as given in his former communication. He has, however, recently succeeded in preparing some fresh specimens of artificial rubies by the same process, but with a higher density, namely 3'7; this number is only 0-25 lower than the native ruby, and he thinks it probable that the true density of the ruby might be attained if the frothing, which takes place to a greater or less degree under the intense heat of the oxyhydrogen blowpipe, could be completely avoided—Vida “ Chemical News,” August 29.

Hungarian T ramylvanian Dacites.—These would appear, from the recent researches of Herr Dr. C. Doelter (“Verhandh der Geol. Reichsanstalt,” 1873, No. 6, 107), to be mostly hornblende and augite audesites, the former always having quartz as an essential constituent, the latter appearing to be mostly free from this mineral. The essential constituents of the dacites are a plagioclase felspar, quartz, sanidine, hornblende, biotite, augite, magnetite, and apatite, the accessory minerals being chlorite and epidote. The quartz occurs as crystals in dihexagonal pyramids, and in grains for the most part porphyritically distributed. Sanidine is a constant constituent in all varieties of the dacites, varying in amount from ten to twenty-five per cent. of the whole of the felspars, and is usually distributed in a fine state of division through the ground-mass. The structure of the quartz-bearing andesite (hornblende andesite) admits of its being divided into three groups -—granitoporphyritic, porphyritic, and trachytic, the latter much resembling the true trachyte. The sanidine in these varieties never exceeds in amount fifteen per cent. of the felspar; the hornblende crystals are very distinct and terminated at both ends, and augite is often present.

Soldering Iron and Steel.—It appears from a paper published by Herr Rest in the “Bayerisches Industrie- und Gewerbe-Blatt," that so-called German silver may be applied to soldering steel to iron and iron to copper.

Borax should be used as a flux, and the German silver granulated as is done for hard brass solder.

The Mechanical Properties of Bronzea—In a paper in the “Comptes Rendus," M. Tresca arrives at the conclusion that there are bronzes more homogeneous, ductile, resistant, and elastic than those produced in the State foundries; and he calls on the Artillery Department to examine the products of private works so as to determine the bronze most serviceable for cannon.

Action on Iron Pipes of the Sulphur contained in Water.—An important notice of this peculiar effect is given in a paper by Dr. E. Priwoznik in a late number of “ Dingler’s Polytechnic Journal.” It appears that when the iron mains conveying the mineral water from a source near Hainburg, Austria, were taken up after having been for more than a dozen years underground, the iron thereof had been strongly acted upon, as exhibited by the difference in structure upon the fracture. On being analysed, the author found the interior layer to consist, in 100 parts, of—Hydrated oxide of iron [(Fe,),O,(OH)6], 81'08; free sulphur, 12-29; sulphuret of iron, 4-48; hygroscopic water, 0'57; nickel, cobalt, magnesia, silica, traces of carbon, and chlorides of ammonium and sodium, 1'58. The second layer was found to contain only 792 per cent. of iron, but no sulphuret or excess of carbon was discovered ; while the third outermost layer was almost pure cast-iron.

A New Mineral T rautwinite.—In the “ Proceedings of the Academy of Natural Science of Philadelphia ” (1873, p. 9), Mr. E. Goldsmith has given this name to a green mineral occurring in microscopic hexagonal crystals (pyramids with the prism, the latter sometimes three-sided) on chromite from California, specimens of which he received from Mr. John O. Trautwine. Chemical and blowpipe examination showed that it contained oxides of chromium, iron and magnesium. Heated to redness in the closed glass tube, it gave a little water and turned bluish green. Not dissolved in acids.

MICROSCOPY.

A Fact agaimt Spontaneous Generation—One of the most important papers for some time contributed to Natural Science is that in the “ Monthly Microscopical Journal " for August, by Messrs. Dallinger and Drysdale, entitled “Researches on the Life History of a Oercomonad.” These authors have done what has not been done before. They have, with the highest objectives and the utmost patience, completely watched the entire development of the creature at which they were working. They have “ continuously examined, during sometimes as long a period as fourteen days, a peculiar monad, hitherto undescribed, but which is under some circumstances developed in enormous quantities in the fluid resulting from the maceration of the head of the cod. This form passes through a remarkable series of changes, each of which might be taken for a distinct and independent creation were not its evolution perfectly regular. Whilst working on this they observed a second form, which possessed only one flagellum instead of two.